<!DOCTYPE html>
<html>

<head>
    <meta charset="UTF-8" />
    <title>setInterval/clearInterval example</title>
    <script type="text/javascript">
    var nIntervId;

    function changeColor() {
        nIntervId = setInterval(flashText, 500);
    }

    function flashText() {
        var oElem = document.getElementById("my_box");
        oElem.style.color = oElem.style.color == "red" ? "blue" : "red";
    }

    function stopTextColor() {
        clearInterval(nIntervId);
    }
    </script>
</head>

<body onload="changeColor();">
    <div id="my_box">
        <p>Hello World</p>
    </div>
    <button onclick="stopTextColor();">Stop</button>
</body>

</html>
